3 - The concept of elementarity and nuclear forces

Summary

Up to this point I have talked mainly about gravity and electromagnetism, which were the only known physical forces up to the early part of this century.

I should now talk of the two further forces, the two nuclear forces – which were discovered during this century and which Einstein (and Dirac for that matter) consistently ignored.

The nuclear forces are of two types, the so-called “weak” and “strong”. Before I discuss them, knowledge of the elementary entities which interact via these forces will be required.

The concept of elementarity of matter is something that has evolved as time has gone by. Of the four Greek “elementary” entities, three (earth, water and air) could be called “elementary” entities of matter, while the fourth (fire) represented a force. If one was working in 1888, say, one would think of atoms as the fundamental elementary particles of the day, and chemistry as the science of elementary particles.